In the external fixation industry, it is often necessary to realign, reposition, and/or securely hold two bone elements relative to one another. For example, in the practice of medicine, bone fragments and the like must sometimes be aligned or realigned and repositioned to restore boney continuity and skeletal function. External fixators may be utilized for this purpose, e.g., such fixators may be used to treat several injuries and/or deformities, including: acute fractures of the skeleton, soft tissue injuries, delayed union of the skeleton when bones are slow to heal, nonunion of the skeleton when bones have not healed, malunion whereby broken or fractures bones have healed in a malposition, congenital deformities whereby bones develop a malposition, and bone lengthening, widening, or twisting.
Generally, the external fixation market can be divided into two major segments: (1) acute trauma, and (2) reconstructive. The customers, products, and needs of each segment may vary widely. Specifically, the trauma segment is dominated by modular fixators. These frames are generally characterized by very rapid application, and, consequently, are known for being fairly simple products. Typically, most of these frames are used for temporary fixation and quite often are only on the patient for hours or days.
The reconstructive segment leans heavily toward ring fixation. Ring fixators, such as the well known Ilizarov frame, are very popular. Such frames are shown in U.S. Pat. Nos. 4,365,624; 4,615,338; 4,978,348; 5,702,389; and 5,971,984, the disclosures of which are hereby incorporated by reference in their entireties. Ring fixators can accomplish a full six degrees of freedom and, when applied and managed well, can aid the correction of primary deformities while not creating secondary deformities. However, mastery of the products themselves and related techniques for use can be a long and daunting process that is not attractive to many users.
In particular, during treatment via an external fixator, potentially of the type described above, the fixator is typically adjusted over a period of time (e.g., during treatment) to reposition bone segments. This adjustment may be implemented according to a “prescription” or correction plan. For example, physicians may adjust an external fixator at precise times over a period of treatment (e.g., on a daily basis for three weeks). Patients, however, may not desire to visit the physician's office every time an adjustment is needed. For this reason, many external fixators can be adjusted by the patients themselves without the assistance of a physician. Adjustment of the external fixator in this manner should nonetheless strictly comply with a predetermined correction or “prescription” plan. On some occasions, however, patients may not adjust their external fixator according to the correction plan for a variety of reasons. For instance, patients may not understand how to use the external fixator correctly. In addition, when the patients themselves adjust the external fixators, physicians may not even know whether patients are in fact adjusting the external fixators according to the correction plan.
To ensure that a particular correction plan is adhered to, it is beneficial for a user (e.g., the surgeon or the patient, depending) to be able to determine the angle between a strut of the external fixator and a ring (or rings) to which the strut is attached. For instance, an external fixation frame, potentially of the Ilizarov-type described above, may include struts, which are aligned at a particular angle with respect to a ring (or rings) used in the frame. Thus, to ensure proper healing and/or correction of a deformity, a user of the frame (e.g., the surgeon or patient) may need to determine such angles. Periodically, these angles may also be modified so as to conform to a predetermined correction plan, as noted above.
As such, it is an object of the present invention to provide improved devices and methods for measuring the angle between two or more points on an external fixation frame and for adjusting an external fixation frame using such devices.